Depressuring valve



Sept- 25, 1962 P. c. JURS ETAI.

DEPRESSURING VALVE 2 Sheets-Sheet 1 Filed June 26, 1959 .3 u l4 49 YVERNON 4. FLETCHER,

PET E R C U u Rs JOSEPH R VANOVERVEEIU INVENTORS :FIE l ATTOE/UE ysSept- 25, 19 2 P. c. JURS ETA].

DEPRESSURING VALVE 2 Sheets-Sheet 2 Filed June 26, 1959 rIIEI I VERNON4. Fara/15g, PETE R C. J u R s JOSEPH PVANOVERVEEN INVENTORS ATTOPA/EYSUnited States Patent Ofllice 3,055,629 DEPRESSURING VALVE Peter C. Jurs,Oakland, Joseph P. Van Overveen, Lafayette, and Vernon A. Fletcher,Oakland, Calif., assignors to Shand and Jurs Company, Berkeley, Calif,

a corporation of California Filed June 26, 1959, Ser. No. 823,191

1 Claim. (Cl. 251-25) This invention relates generally to valves andvalve systems suitable for depressuring operations. More particularly,the invention pertains to depressuring apparatus applicable to storageand process vessels.

Many products are commonly stored in pressure tanks or vessels. Forexample, liquified petroleum products are stored in pressure tanks at apressure dependent upon that of the temperature and vapor pressure ofthe liquified components. For example, with liquified butane or propane,the normal tank pressure may range from approximately 30-200 psi. fortemperatures ranging from 70 It is customary to provide storage tankswith pressure relief valves whereby when the internal tank pressurereaches a predetermined value, the relief valve opens automatically tovent ofl? vapor. This serves to protect the tank against excessiveinternal pressure which might cause serious injury. However, situationshave arisen in which such relief valves have been found inadequate torelieve the excess pressure created within the tank. For example, in theevent of a fire in the vicinity of a storage tank, the contents may beheated considerably above normal temperatures so that the relief valveand the piping connected to the tank are inadequate to carry off thevapor at a suflicient rate to properly protect the tank againstexcessive pressure.

Even if a number of conventional safety relief valves are provided onthe tank, such protection is still inadequate because the flame from afire may impinge only a certain portion of the tank to cause overheatingof a localized area of the tank. Within a relatively short period oftime, this weakens the metal of the tank so that the tank starts tobulge or blister in this area, after which a rupture often occurs. Insuch a situation, the conventional safety relief valves will not operatebecause the pressure in the tank may still be below the safety limitsfor the tank.

In process vessels such as cracking towers and the like, something may'go wrong with the process so that the pressure within the processvessel approaches an unsafe limit. Heretofore, when this has occurred,it has been the normal procedure to shut down the entire process. As iswell known, this is a very costly procedure. There is, therefore, a needfor means for depressuring the process vessels for a short period oftime so that a cushion of time is obtained to find out what is wrongwith the process.

In general, it is an object of the present invention to provide improvedmeans for rapidly depressuring vessels used for processing and storage.

Another object of the invention is to provide a simplified and reliabledepressuring valve which can be operated in emergencies and which is notvulnerable to damage.

Another object of the invention is to provide a depressuring apparatusof the above character which may in- 3,055,629 Patented Sept. 25, 1962clude means responsive to the wall temperature of the storage vessel tosecure emergency tank venting.

Another object of the invention is to provide a depressuring valve ofthe above character which can be utilized for a large range of pressuresand temperatures.

Another object of the invention is to provide a depressuring valve ofthe above character in which an excellent seal is obtained.

Another object of the invention is to provide a depressuring valve ofthe above character which opens and closes very rapidly.

Another object of the invention is to provide a depressuring valve ofthe above character in which dynamic and static pressures are utilizedto obtain rapid repressuring of the valve.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiment has been setforth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a cross-sectional view of a depressuring valve incorporatingthe present invention.

FIGURE 2 is a detail view taken along the lines 22 of FIGURE 1.

FIGURE 3 is a view partially in cross-section showing the depressuringvalve incorporated in a system with a control valve in one position.

FIGURE 4 is a partial view similar to that shown in FIGURE 3 with thecontrol valve in a different position.

As shown in FIGURE 1, our depressuring valve consists of a body 11 whichis provided with a vertical passage 12 adapted to be connected to thestorage or pressure vessel by a fitting 13. The valve body is providedwith two stationary radially spaced concentric valve seats 14 and 16which lie in a substantially horizontal plane. The valve seats areprovided with inserts 17 of suitable valve seat material such asstainless steel. The valve seats 14 and 16 are separated by an annularpassage .18 which communicates with an outflow passage 15 that isadapted for connection to suitable means such as a venting pipe (notshown). An annularly contoured pallet '19 overlies the valve seats 14and 16 and is adapted to seal upon the valve seats 14 and 16.

A dome-like cover 21 encloses the space 20 overlying the pallet 19 andis secured to the valve body 11 by suitable means such as stud 23. Theinterior of the cover 21 is machined to provide a cylindrical guidesurface 24 which is only slightly larger in diameter than the diameterof the pallet .19. A limiting shoulder 26 also machined within the cover21 forms a limiting stop for engaging the pallet when the latter is infull open venting position as hereinafter described. The upper part ofthe dome cover is provided with an opening 27 for communicating with acontrol pipe 28 threaded into the cover.

The pallet 19 includes a metal plate 31 which is provided with a centralopening 32. A relatively thin, flexible impervious diaphragm 33 ofsuitable material such as stainless steel is provided as a facing on thelower side of the plate 31. In certain applications a nonmetallic orsynthetic material can be used for the diaphragm. As shown, thediaphragm 33 covers the entire bottom surface of the plate and has itsouter margins clamped to the plate by suitable means such as a clampingring 34 secured to the plate 31 by bolts 36. It will be noted that theclamping ring 34 is radially spaced outwardly from the outer valve seat16 so that the diaphragm 33 may readily engage the valve seats.

An elbow 37 is mounted on the body in the passage 12 and facesdownwardly into the passage 12. The elbow 37 is adapted to connect to acontrol pipe 38 threaded into the side Wall of the body.

In FIGURE 3, the depressuring valve is shown incorporated in a system inwhich the control lines 28 and 38 are connected to a suitable controldevice such as a three-way valve 41 which is schematically illustrated.The three-way valve consists of a body 42 and a movable valve member 43which is provided with a T-shaped passageway 44. The T-shaped passagewayis adapted to communicate with openings 46, 47 and 48 in the body 42.The opening 46 is connected to the control pipe 38 and the opening 47 isconnected to the control pipe 28. The opening 48 is connected to a pipe51 which opens to the atmosphere.

As shown in FIGURE 3, the depressuring valve is mounted on a vessel ortank 52 by the fitting 13.

In FIGURE 4, the control line 38 is shown directly connected to the tankrather than to the valve.

Operation of the depressuring valve and system described above is asfollows. Normally, the valve 41 is positioned so that the pipes 28 and38 are interconnected. Under such a condition, the pressure in the domechamber 22 assumes the same value as that in the tank because the tankpressure is directly applied to the dome through the interconnectedpiping 38 and 28. The pressure in the dome chamber 22 acts downwardlyupon the pallet 19 over an area corresponding to the mean effectivediameter of the annular seat 16. Since this area is substantiallygreater than that corresponding to the effective diameter of the seat14, the pallet 19 is normally urged downwardly into sealing engagementwith both seats 14 and 16.

The tank pressure also passes through the opening 32 in the metal plate31 and between the diaphragm 33 and the metal plate. This pressure has atendency to cause flexing of the portion of the diaphragm 33 whichoverlies the annular passage 18 as shown particularly in FIG- URE 2.This occurs because the annular passage 18 is exposed to the atmospherethrough the outflow passage 15. This differential in pressure causes theslight bulging of the diaphragm shown in FIGURE 2. This bulging of thediaphragm helps to establish an effective seal between the two seatrings 14 and 16.

Now let it be assumed that an over-pressure condition occurs in the tankor vessel 52 and that it is desired to depressure the vessel. This isaccomplished by moving the movable member 43 to a position so that line28 is connected to line 51 to freely vent the dome chamber 22 to theatmosphere. This sudden reduction of pressure in the dome chamber causesthe pressure in the vertical passageway 12 to actually pop the pallet 19upwardly into a position in which it rests against the annular shoulder26. The tank is then freely vented through the passage 12, the annularpassage 18 and out through the outflow passage 15.

Now let it be assumed that the pressure in the tank has been reduced toa safe value and that it is desired to close the depressuring valvebefore the tank pressure has been reduced to atmospheric. The valve 41is then actuated to again interconnect pipes 28 and 38. At the time thevalve 41 is moved to this position, the vapors are still passing throughthe vertical passage 12. Certain of these moving gases or fluids aretrapped by the downwardly facing elbow 37 and pass into the dome chamber22. By utilization of the downwardly curved elbow 37, it is apparentthat the dynamic as well as static pressure is applied to the domechamber 22. Since the pressure in the dome chamber 22 rapidly assumesthe same value as in the passage 12, the pallet 19 almost instantlymoves to a closed position in sealing engagement with the seat rings 14and 16. Thus, it can be seen that by the movement of the valve 41between the two positions shown, the depressuring valve is rapidly movedbetween sealing and venting positions.

It will be evident from the foregoing that the depressuring valve andsystem has many applications in which it can be used. The valve 41 canbe controlled in any suitable manner. For example, the valve can becontrolled locally or remotely by mechanical, electrical, hydraulic orpneumatic means that is manually or automatically actuated. Switches,fusible plugs and other types of sensing devices can be utilized todetermine when the valve should be open and closed. The depressuringvalve, in particular, has been found to be useful for protecting storagetanks containing liquified petroleum products. Because of the relativelylarge venting passages provided, the storage tank pressure is droppedvery rapidly without danger of bursting the tank although the tank maybe in or near a fire. The depressuring valve is also particularly usefulin certain processes in which process vessels or tanks are utilized.When it is noticed that a dangerous pressure is being produced in aprocess vessel, the pressure in the process vessel may be rapidlyreduced by venting the vessel to the atmosphere through the depressuringvalve. As soon as the pressure in the tank has reached a safe limit, thedepressuring valve can be repressured or closed. This will provide acushion of time in which an analysis can be made to determine what hasoccurred in the process to cause the elevated pressure in the processvessel. If the trouble is not discovered before the pressure again risesto a dangerous level, the pressure vessel can again be depressurized.The same procedure can be followed until the trouble in the process hasbeen eliminated. This is a much more economical way of finding a troublein the process rather than shutting down the process.

Although the pallet 19 has been described as having a central opening32, if desired the central opening can be eliminated when it is notdesired to apply pressure between the diaphragm and the pallet. Althoughthe depressuring valve has been described utilizing the pressure fromthe tank or vessel to which the valve is connected, it is readilyapparent that if desired an external source of pressure such as plantair or bottled nitrogen can be utilized for maintaining the pallet in aclosed position.

Since the use of conventional diaphragms such as rubber or otherresilient material has been eliminated, the diaphragm is not likely tobe injured or fail at high temperatures. However, where the valve isunlikely to be exposed to heat, conventional diaphragms of rubber orother resilient material may be utilized. In addition, when thediaphragm is formed of stainless steel, the valve itself can be utilizedin process or storage vessels containing vapors which would normallyattack conventional diaphragms. The valve itself is quite simple inconstruction and very reliable in its operation. For a given size, ithas a relatively high venting capacity.

We claim:

In a depressuring valve adapted to open to vent fluid from a pressuresystem, a body having an inlet passage for connection with a source offluid pressure and having a venting discharge passage, a pair ofradially spaced concentric seats formed within the body, the openingthrough the inner seat being in communication with the inlet passage andthe opening between said seats being in communication with the dischargepassage, a pallet having one side of the same adapted to seat and sealupon both of said spaced concentric seats, said pallet including a rigidannularly contoured plate, an impervious, relatively thin flexiblediaphragm mounted on the lower face of said plate, means securing anouter annular portion of said diaphragm to said plate, means forming afluid chamber on the other side of the pallet, the plate being formedwith an opening extending therethrough and communicating between thechamber and the adjacent surface of the diaphragm to apply the fluidpressure in the chamber to the diaphragm whereby the annular portion ofthe diaphragm References Cited in the file of this patent between theseats bulges to form tight sealing engagement UNITED STATES PATENTS withthe radially spaced seats, means external of the body providingcommunication between the inlet passage and 1 22: 5:? lg the closedchamber to permit rapid fluid flow between the 5 2O64343 Finley 1936inlet passage and the closed chamber to rapidly move the 2417994 sheets1947 pallet to a closed position when the pallet is in an open 2:456:9131943 position and to maintain the pallet in a closed posi ion 2,480,712Carbon Aug 30, 1949 after it has been moved to a closed position, andmeans 557,53 Dram et 1 June 19, 1951 for venting the chamber to theatmosphere for permitting 10 2,577,967 Hughes Dec. 11, 1951 the fluidpressure within the inlet passage to rapidly move 2,732,856 Jurs J an.31, 1956 the pallet from a closed to an open position. 2,882,006Reinecke Apr. 14, 1959 2,928,413 Hansen Mar. 15, 1960

